Electric arc fuse wire additive manufacturing bainite steel strengthening process method

Abstract

The invention discloses an arc fuse additive manufacturing bainite steel strengthening process method which comprises the steps that S1, additive manufacturing materials including a heat source, a welding wire and shielding gas are prepared; s2, various parameters in the additive manufacturing process are preset, wherein the parameters comprise dry elongation, air flow, advancing speed and wire feeding speed; s3, an additive manufacturing deposition strategy is adopted in the additive manufacturing process, additive printing is carried out according to a preset printing path, an infrared thermal imager is used for temperature detection, and when the material is cooled to 100 DEG C or 300 DEG C, next printing is carried out; and S4, 50 layers are deposited, the interlayer retention temperature of each layer is controlled to be reduced to a set value, and the material increasing sample is completed. According to the method, the workpiece can be baked in the manufacturing process, another step of treatment is not needed, and bainite steel strengthening can be completed in the additive manufacturing process.

Description

Technical Field

[0001] The present application relates to the field of additive manufacturing technology, and more specifically to a method for strengthening bainitic steel by additive manufacturing using an arc fuse. Background Art

[0002] High-strength low-alloy steel (HSLA) is micro-alloyed with Ti, V, Nb and Al, with a total weight percentage of less than 2.5wt%, a weight percentage of C less than 0.25wt%, and the remaining elements are composed of iron. Due to its excellent mechanical properties, HSLA steel has been widely used in the preparation of large components and has a dominant position in the shipbuilding, machinery and construction industries. In recent years, with the continuous development of Metal Additive Manufacturing (MAM) technology, the wire arc Additive Manufacturing (WAAM) technology developed on the basis of Directed Energy Deposition (DED) has the characteristics of high deposition rate, short production time, low raw material cost, low equipment cost, flexible part size and high efficiency. It has great prospects in application. In addition, due to the excellent weldability of HSLA steel, the prospect of combining it with wire arc Additive Manufacturing technology has become even greater.

[0003] The existing WAAM technology heat source types are mainly divided into three types: gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and plasma arc welding (PAW). Both GTAW and PAW use non-consumable electrodes and independent wire feeding systems. The arc is very stable during the forming process, and the heat input is easy to adjust. However, when using an independent wire feeding system to control the heat input, the wire feeding direction will affect the quality of the workpiece and increase the complexity of the process. GMAW uses consumable electrodes, which are more controllable in the wire feeding direction and the process is simpler; and the deposition rate of GMAW is 3-4kg / h, which is 2-3 times the deposition rate of GTAW or PAW. However, the high deposition rate of GMAW is accompanied by high heat input, which will cause the surface of the deposited workpiece to appear uneven and corrugated, affecting the surface morphology of the workpiece, increasing the later processing allowance, and also increasing the material waste rate.

[0004] CMT technology is a new technology developed on the basis of GMAW technology. Compared with GMAW technology, it has the characteristics of low heat input and small spatter during the deposition process. The performance of the prepared titanium, aluminum, nickel and steel alloys is comparable to that of forged materials and has broad prospects. The heat dissipation process of the components deposited by the CMT-based WAAM technology is dissipated through heat conduction between the deposited sample and the substrate, and forced convection or radiation to the surrounding environment through the protective gas. As the number of deposited layers increases, the heat dissipation conditions change, from the initial conduction heat dissipation to gradually change to conduction plus convection and radiation heat dissipation.

[0005] Arc fuse additive manufacturing bainitic steel strengthening, by controlling the process parameters in additive manufacturing and limiting the interlayer temperature (two temperatures), can achieve the performance enhancement of bainitic steel by using its own temperature change to produce a process similar to baking. In view of the thermal cycle of the WAAM forming process, the study of the thermal cycle of HSLA found that the precipitation and distribution of carbide structure of HSLA steel will change after thermal cycles at different temperatures, and the temperature boundary is the traditional upper limit temperature of baking 200℃. For the sample structure with a temperature above 200℃, the carbide distribution in the sample structure is concentrated and the carbide grains are fine; the carbide distribution in the sample structure below 200℃ is scattered and the carbide grains are relatively large. The scattered carbides pin more ferrite and bainite, and show a pinning effect when an external load is applied, while the concentrated carbide particles pin less bainite and ferrite. Under the condition of external load, the softer phase deforms first and fails to play an overall pinning effect. Therefore, the scattered carbides show a stronger baking effect.

[0006] The baking effect is beneficial to improving the yield strength of the workpiece and is widely used in the automotive industry. However, traditional baking is another step after the sample is processed. It is found that baking treatment will increase the yield strength of the material. After hardening treatment, baking treatment will make carbon use dislocations as rapid diffusion channels and form cementite pinning dislocations on the dislocations. Summary of the invention

[0007] In this embodiment, an arc fuse additive manufacturing bainitic steel strengthening process method is provided to solve the problem in the related art that the workpiece cannot be baked during the manufacturing process and needs further processing in another process.

[0008] An embodiment of the present invention provides an arc fuse additive manufacturing bainite steel strengthening process method, the strengthening process method comprising: S1. Additive manufacturing material preparation, including heat source, welding wire and shielding gas; S2. Presetting various parameters in the additive manufacturing process, including dry extension length, gas flow, travel speed, and wire feeding speed; S3. During the additive manufacturing process, an additive manufacturing deposition strategy is adopted, and additive printing is performed according to a preset printing path. The temperature is detected by an infrared thermal imager. When the material cools to 100°C or 300°C, the next printing is performed. S4. Deposit 50 layers, control the dwell temperature between each layer to drop to the set value, and the additive sample is completed.

[0009] In an optional embodiment, in step S1, the welding wire is ER120S-G and the shielding gas is 82% Ar+18% CO2.

[0010] In an optional embodiment, in step S2, the dry extension length is 11 mm, the air flow rate is 22 L / min, the travel speed is 6 mm / s, and the wire feeding speed is 4.5 m / min.

[0011] In an optional embodiment, in step S3, the deposition strategy in additive manufacturing is left-right complementary cyclic stacking.

[0012] In an optional embodiment, when the material interlayer temperature is 100° C. or 300° C., the strength of the additive sample is bottom>middle>top.

[0013] In an optional embodiment, when the material interlayer temperature is 100° C. or 300° C., the elongation trend of the additive sample is top>middle>bottom.

[0014] In an optional embodiment, when the material interlayer temperature is 100° C., the yield strength of the additive sample at the bottom is 730.53 MPa, the yield strength in the middle is 636.06 MPa, and the yield strength at the top is 580.86 MPa.

[0015] In an optional embodiment, when the material interlayer temperature is 100°C, the total elongation of the additive sample increases from 23.63% at the bottom to 27.09%. The ultimate tensile strength gradually decreases from 769.86MPa at the bottom to 708.99MPa at the top, and the total elongation increases from 23.63% at the bottom to 27.09% as the deposition height increases.

[0016] In an optional embodiment, when the material interlayer temperature is 300°C, the yield strength of the additive sample is 451.64 MPa at the top, 448.84 MPa in the middle, and 531.91 MPa at the bottom, and the ultimate tensile strength gradually decreases from 770.86 MPa at the bottom to 747.68 MPa. As the deposition height increases, the total elongation increases from 16.02% at the bottom to 26.69%.

[0017] Compared with the prior art, the arc fuse additive manufacturing bainite steel strengthening process method of the present invention has the following beneficial effects: The method can bake the workpiece during the manufacturing process without the need for another processing step, and can complete the strengthening of bainite steel during the additive manufacturing process.

[0018] Specifically, in terms of yield strength, the workpiece bottom > middle > top; in terms of elongation, the top > middle > bottom. At 100°C, there is an obvious yield platform at the bottom and middle; at 100°C, the top and 300°C bottom yield discontinuously; at 300°C, the middle and top yield continuously; In terms of mechanical conditions of the gain effect, for samples with interlayer temperatures of 100℃ and 300℃, the overall change trend of the yield strength of the samples is bottom> middle> top, and the trend of elongation is top> middle> bottom. The yield strength of the 100℃ sample drops from 730.53MPa at the bottom to 636.06MPa in the middle, and then to 580.86MPa at the top. With the increase of deposition height, the yield strength decreases significantly; the total elongation increases from 23.63% at the bottom to 27.09%. The yield strength of the 300℃ sample is 451.64MPa at the top, with an abnormal phenomenon of 448.84MPa in the middle, and the highest at the bottom, which is 531.91MPa; the ultimate tensile strength gradually decreases from 770.86MPa at the bottom to 747.68MPa. With the progress of deposition height, the total elongation increases from 16.02% at the bottom to 26.69%, which is a significant increase.

[0019] In general, when the interlayer temperature is controlled at 100°C for component deposition, the yield strength is enhanced. Comparing the yield strength of components with different interlayer temperatures at the same deposition height, at the top, the yield strength is 130MPa higher than that of the component with an interlayer temperature of 300°C, and this is the lowest yield strength increase. The yield strength increase is more obvious at a lower deposition height. At the same time, it can also ensure that the plasticity of the component with an interlayer temperature of 100°C is in a relatively stable area. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a flow chart of a process method for strengthening bainite steel by additive manufacturing of arc fuse in an embodiment of the present invention; Figure 2 A schematic diagram of a printing process using a deposition strategy in additive manufacturing in an embodiment of the present invention; Figure 3This is a macroscopic diagram of the baking temperature for additive manufacturing in an embodiment of the present invention; Figure 4 This is a graph showing the changes in the structure (grain size) of the additively manufactured baked strengthening structure in an embodiment of the present invention; Figure 5 This is a graph showing the change of the baking strengthening structure (cementite content) of additive manufacturing in an embodiment of the present invention; Figure 6 This is a graph showing the change of the additive manufacturing baking strengthening structure (dislocation density) in an embodiment of the present invention; Figure 7 This is a diagram showing the changes in the additive manufacturing baking strengthening structure (engineering stress-strain curve) in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meaning understood by people with general skills in the technical field to which this application belongs. The words "one", "a", "the", "these" and the like in this application do not indicate a quantitative limitation, and they may be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusions; for example, a process, method and system, product or device comprising a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" may mean: A exists alone, A and B exist at the same time, and B exists alone. Generally, the character " / " indicates that the objects associated with each other are in an "or" relationship. The terms "first", "second", "third", etc. in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0024] In an embodiment of the present invention, a method for strengthening bainite steel by additive manufacturing of arc fuse is provided. Figure 1 Flow chart of the arc fuse additive manufacturing bainite steel strengthening process of the present invention, as shown in Figure 1 As shown, the process includes the following steps: S1. Preparation of additive manufacturing materials, including heat source, welding wire and shielding gas. In this embodiment, the welding wire is ER120S-G, the shielding gas is 82% Ar+18% CO2, and the heat source mode is CMT. S2. Preset various parameters in the additive manufacturing process, including dry extension length, air flow rate, travel speed and wire feeding speed; in this embodiment, the dry extension length is 11 mm, the air flow rate is 22 L / min, the travel speed is 6 mm / s, and the wire feeding speed is 4.5 m / min.

[0025] S3, in the additive manufacturing process, an additive manufacturing deposition strategy is adopted, and additive printing is performed according to a preset printing path, and temperature detection is performed using an infrared thermal imager. When the material cools to 100°C or 300°C, the next printing is performed; in step S3, if Figure 2 As shown, the deposition strategy in additive manufacturing is left-right complementary cyclic stacking; and the inter-layer height of the stack is 2 mm.

[0026] S4. Deposit 50 layers, control the dwell temperature between each layer to drop to the set value, and the additive sample is completed.

[0027] Combination Figures 3 to 6 As shown, it should be noted that when the material interlayer temperature is 100°C or 300°C, the strength of the additive sample is bottom>middle>top.

[0028] When the material interlayer temperature is 100℃ or 300℃, the elongation trend of the additive sample is top > middle > bottom.

[0029] When the material interlayer temperature is 100 °C, the yield strength of the additive sample is 730.53 MPa at the bottom, 636.06 MPa in the middle, and 580.86 MPa at the top.

[0030] When the material interlayer temperature is 100 °C, the total elongation of the additively manufactured sample increases from 23.63% at the bottom to 27.09%.

[0031] When the material interlayer temperature is 300°C, the yield strength of the additive sample is 451.64MPa at the top, 448.84MPa in the middle, and 531.91MPa at the bottom. The ultimate tensile strength gradually decreases from 770.86MPa at the bottom to 747.68MPa. As the deposition height increases, the total elongation increases from 16.02% at the bottom to 26.69%.

[0032] As a first embodiment of the present invention, when the material interlayer temperature is 100°C, the strength of the additive sample is bottom>middle>top. The elongation trend of the additive sample is top>middle>bottom. The yield strength of the additive sample is 730.53MPa at the bottom, 636.06MPa at the middle, and 580.86MPa at the top. The total elongation of the additive sample increases from 23.63% at the bottom to 27.09%.

[0033] As another embodiment of the present invention, when the material interlayer temperature is 100°C, the strength of the additive sample is bottom>middle>top. The elongation trend of the additive sample is top>middle>bottom. The yield strength of the additive sample is 451.64MPa at the top, 448.84MPa in the middle, and 531.91MPa at the bottom. The ultimate tensile strength gradually decreases from 770.86MPa at the bottom to 747.68MPa. As the deposition height increases, the total elongation increases from 16.02% at the bottom to 26.69%.

[0034] From the above, it can be seen that the best embodiment is when the temperature between the material layers is 100°C. Figures 3 to 6 As shown, the process method can be used to bake the workpiece during the manufacturing process without the need for another step of treatment. The bainitic steel can be strengthened during the additive manufacturing process, and the strengthening effect when the material interlayer temperature is 100°C is greater than the effect when the material interlayer temperature is 300°C.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for strengthening bainitic steel by arc fuse additive manufacturing, characterized in that: The strengthening process method comprises: S1. Additive manufacturing material preparation, including heat source, welding wire and shielding gas; S2. Presetting various parameters in the additive manufacturing process, including dry extension length, gas flow, travel speed, and wire feeding speed; S3. During the additive manufacturing process, an additive manufacturing deposition strategy is adopted, and additive printing is performed according to a preset printing path. The temperature is detected by an infrared thermal imager. When the material cools to 100°C or 300°C, the next printing is performed. S4. Deposit 50 layers, control the dwell temperature between each layer to drop to the set value, and the additive sample is completed.

2. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1 is characterized in that: In step S1, the welding wire is ER120S-G and the shielding gas is 82%Ar+18%CO2.

3. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1, characterized in that: In step S2, the dry extension length is 11 mm, the air flow rate is 22 L / min, the travel speed is 6 mm / s, and the wire feeding speed is 4.5 m / min.

4. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1, characterized in that: In step S3, the deposition strategy in additive manufacturing is left-right complementary cyclic stacking.

5. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1, characterized in that: When the material interlayer temperature is 100℃ or 300℃, the strength of the additive sample is bottom>middle>top.

6. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1, characterized in that: When the material interlayer temperature is 100℃ or 300℃, the elongation trend of the additive sample is top>middle>bottom.

7. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1, characterized in that: When the material interlayer temperature is 100°C, the yield strength of the additive sample is 730.53 MPa at the bottom, 636.06 MPa in the middle, and 580.86 MPa at the top.

8. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1, characterized in that: When the material interlayer temperature is 100 °C, the total elongation of the additively manufactured sample increases from 23.63% at the bottom to 27.09%.

9. The arc fuse additive manufacturing bainite steel strengthening process method according to claim 1, characterized in that: When the material interlayer temperature is 300°C, the yield strength of the additive sample is 451.64MPa at the top, 448.84MPa in the middle, and 531.91MPa at the bottom. The ultimate tensile strength gradually decreases from 770.86MPa at the bottom to 747.68MPa. As the deposition height increases, the total elongation increases from 16.02% at the bottom to 26.69%.

Images